So last year, the pop star turned to Tristan Herbert, a 23-year-old Parkville artist who makes custom covers for iPhones and Androids. Herbert spent 11 hours designing a case with a drawing of Minaj sporting long blonde hair, big hoop earrings, a belly shirt and blazer. The words "Pink Friday," the title of Minaj's first album, run alongside, and the background is, of course, pink. Minaj's people said it was "amazing," and Herbert, then a largely unknown artist, had his first big client.

"Seeing her with the case is amazing," Herbert said. "It's kind of surreal."

Since starting his company, Tristan Art, about eight months ago, Herbert has designed more than 400 cases. His clients include Detroit Lions tight end Brandon Pettigrew, Joe Budden from the reality show "Love & Hip Hop New York," cast members of "Bad Girls Club" and DJ Clue.

Herbert's customers send him pictures of people and faces they want on their cell phone cases, and he illustrates them on his desktop computer. There are few plain white backgrounds — Herbert prefers collages with bursts of color.

"I actually get mad when people ask me, 'Can you just do this and put it on the white case?'" he said. "They don't give me the freedom, really, to do what I want to do."

He hasn't been doing it long. Before he started, he was adrift; he had moved to Baltimore in 2011 to train for soccer, but later realized a torn meniscus would keep him from making a career out of it.

"He wasn't depressed, but he wasn't happy," said his older sister, Nerisha Herbert.

When Herbert's little brother Jamari came to visit him last summer, Tristan asked him, "'What do you see, when you see me?'"

His brother responded, "I just see my big bro."

Jamari didn't see Herbert as someone to look up to — someone he wanted to be like when he grew up, Herbert said, which stung.

"I was like, 'Man, I've got to get it together,'" Herbert said.

Herbert had always been interested in art; he wanted to draw a cartoon series that one day might air on Nickelodeon, he said. Art classes were required at Pendleton High School, in Pendleton, S.C., which he attended, but unlike many of his classmates, he enjoyed them, he said.

Herbert didn't go to college — immediately after high school, he worked for his father in a fabric warehouse, Kravet Fabrics, in South Carolina.

Since he couldn't afford to go to art school, Herbert began to teach himself how to draw cartoons on his computer through trial and error.

"In this eight-month span, I learned what probably would have taken two or three years [in school]," he said.

At first, it wasn't easy going. Herbert admits his early drawings were "horrible."

"I did a picture of Michael Jordan," he said, "and somebody told me they thought it was Shaq."

As he made them, Herbert would post his designs on Instagram, soliciting feedback from others. Soon, people began asking him to draw illustrations. One day in August, Herbert and his brother, Jason, were walking through New York, and Herbert was looking at his Gameboy cell phone case. Staring at his phone, he realized he could add his own designs to cell phone cases.

Not long after he started making them, Herbert's cell phone cases "took off through the roof," he said. The number of people who followed Herbert on Instagram ballooned from 200 to more than 25,000.

"People are like 'This is something I've never seen before, I would love to be a part of this,'" he said.

A'riel Tapplin, 23, of Columbia, S.C., saw Herbert's work on Instagram and Twitter, and ordered a case featuring her and her boyfriend.

"Everybody always asks me [about it]," she said. "I don't have to worry about anyone else having the same case as me."

A member of Minaj's entourage was dating a girl Herbert knew, and showed Minaj some of Herbert's work on Instagram. When he got the message saying Minaj wanted one of his cases, Herbert thought it was his brothers playing a joke on him. Once Minaj had one, other celebrities came calling.

Personalized cell phone cases are in high demand, said David Petr, creative director for Caseable, a company which allows customers to create their own cases for items like smart phones, laptops and iPads. Users can upload their own images, insert text and select add-on features.

"A lot of people like the idea of having something custom designed for themselves these days," Petr said. "It's kind of like an expression of personal style."

The market for custom cell phone cases is "pretty saturated," Petr said. What sets them apart is how they allow people to customize their cases and how they encompass the different aspects of design. Companies such as M-Edge, based in Odenton, offer lines of cell phone and tablet covers, which come in different textures and colors.

Two years ago, Caseable had a similar start to Herbert (Petr is an alumnus of the Maryland Institute College of Art), and now it has offices on two continents. Herbert is "off to a good start," Petr said.

"His products are definitely unique in their own way, and it has his personal style," Petr said. "If it is catching on in a personal crowd, it will keep spreading by word of mouth and social networking."

When he first started making the cases, Herbert sent his designs to a company to print them, but began making the cases himself after he was able to purchase the necessary supplies.

Herbert's iPhone cases, which once sold for $35, are now $100. They're his most popular item, though he also designs iPad cases, laptop skins, playing cards, key chains. (Not wanting a lawsuit from Warner Bros., he only made one cell phone case with Bugs Bunny and Taz on it, which he keeps for himself.) He's also developing standard designs for phone cases, and also launching a clothing line.

Most of Herbert's customers are female, but he thinks the clothing line will bring in more male customers. He's working with colors that match new shoes, so guys can have something to go with, say, the new pair of Air Jordans. He can be a shameless self-promoter.

"Sometimes if I'm just in the mall, and I'm just sitting around in the food court, I'll go up to [someone with an iPhone] and say 'Hey, who made your case?' or 'Do you have a case? I make custom cases,'" Herbert said. "I'm not shy."

Herbert has a strong support system of friends and family. When he was out of work, his brothers urged him to fill out job applications. He especially credits his sister Nerisha with helping him when he wanted to give up.

"He would text me at 3 o'clock in the morning sometimes," Nerisha said. "I had to talk to him and tell him, 'Don't give up.'"

To thank her, Hebert sent his sister a case he designed featuring a heel with glitter on it, she said.

"I got it on Valentine's Day," she said. "It almost made me cry."

Besides making cases for his family, Herbert also gives away cases to fans who can't afford them, through contests on Instagram.

As for his little brother, Jamari, Herbert has made him proud — he said his brother had to text him one day to prove to the kids at school that they are actually siblings.

Herbert hopes his connections with celebrities such as Minaj will have more musicians asking for his work. His celebrity wish list includes Taylor Swift, Selena Gomez and Ariana Grande.

"Those are three I've just been dying to make a case for," Herbert said. "I'm checking my email like, 'Please, today is the day.'"

For now, he's focused on expanding his line of accessories.

"I really see myself being a mogul in the future," he said. "That's my goal. Just capitalize off everything that I can possibly do. I don't want to just limit myself to one thing."